Will this circuit really control a HDD motor?

A guy has posted on **broken link removed** (see first schematic) a circuit which he claims will crudely control a HDD stepper motor using a 74ac14 chip (I'm hoping he uses "stepper motor" as a simplification of "3-phase motor"). I don't have the skills to evaluate whether that has any chance of working. So can it? If so I'm going to try and build it; what are the complexities involved?

HDD motors are usually brush-less DC motors, not steppers. Why not use the BLDC driver chip from the hard drive you got the motor from? They were made to work together

It might work (a little bit) but what use is it?
Modern disk drives have a lot of micro involvement with motor control now days. Don't think the drive chip would work.

Thanks for your time. I'd like to use the spindle for this project. I don't need much torque but I'd like to have a steady rpm.

I'm exploring using the controller that comes with the HDD but there are a couple of problems (so far) that I see:

1) It looks like the controller needs to get a signal from the motherboard before it will start the motor. For example, if I connect just the power cable nothing happens until I also plug in the SCSI cable. I have no idea how to fake out the controller to get it started.

2) I'd like to be able to adjust the RPMs. This isn't quite so important but it'll be harder to make my clock accurate if I can't.

3) The controller board gets pretty hot, which means it's using a lot of power. I'm also a bit worried about it over-heating since I won't have a cooling fan.

If anybody knows how to solve those issues then I'd gladly use the supplied controller. (In case it matters, the drive is [was?] a Seagate 120GB Barracuda ST3120026AS.) If the circuit in the OP can get the motor spinning at a constant rate then it might be exactly what I want, especially if I can adjust it by tweaking the pot.

Why use a HDD spindle? One, I like the idea of re-using old parts. More importantly, it looks cool.

You might be better to use a microcontroller to produce the pulses to drive the MOSFETS. If the microcontroller is run from a crystal, the frequency will be very accurate, and you can vary the speed with the delays in the code.

You might be better to use a microcontroller to produce the pulses to drive the MOSFETS. If the microcontroller is run from a crystal, the frequency will be very accurate, and you can vary the speed with the delays in the code.

I think that there are some PICs that have modules designed to produce the timing for motors.

You might look at a motor from an electric clock. I think without gears they run at 600 rpm.

Diver300 said:

You might be better to use a microcontroller to produce the pulses to drive the MOSFETS. If the microcontroller is run from a crystal, the frequency will be very accurate, and you can vary the speed with the delays in the code.

I think that there are some PICs that have modules designed to produce the timing for motors.

Click to expand...

Is this something I can do with an Arduino?

I've been digging around some. Is this what you mean by a microcontroller? https://www.electro-tech-online.com/custompdfs/2010/12/doc8012.pdf

Deeg said:

I've been digging around some. Is this what you mean by a microcontroller? https://www.electro-tech-online.com/custompdfs/2010/12/doc8012-1.pdf

Click to expand...

That is the sort of thing.

That application note shows motor control with feedback, where the voltages generated by the motor are sensed in order to decide when to turn on the next winding. The original circuit with the 74AC14 had no feedback, which is very much simpler but doesn't perform as well.

You are aware that a HDD motor spins at between 3,000RPM to 15,000RPM, depending on the brand/model of the drive,right? With out serious gearing down, you won't be able to see your clock hand, or gears move.

That's one of the reasons I'd like to use a HDD spindle--I have a couple of gears that I'd like to use for effect that will reduce the speed, like a **broken link removed**.

Deeg said:

That's one of the reasons I'd like to use a HDD spindle--I have a couple of gears that I'd like to use for effect that will reduce the speed, like a **broken link removed**.

Click to expand...

The HDD motor doesn't have hardly any torque, all it has to do is spin light plastic disks. A Geneva gear takes some torque to work. Have you looked at other types of motors? Here is a place that has a good assortment, and even some gears and other drive stuff; Motors | AllElectronics.com